1. Field of the Invention
This invention relates generally to an electronic musical instrument and particularly to an automatic rhythm performing apparatus by which a rhythmic tone corresponding to a rhythmic musical instrument having a plurality of tone sources is produced.
2. Prior Art
Among the rhythmic musical instruments, there are some which comprise plural kinds of tone sources. For example, a snare drum is constituted by two kinds of tone sources one of which is a drum and the other of which are snares. The snare drum produces therefore a tone composed of both a drum tone and a snare tone. Similarly, a tambourine produces a tone composed of both a drum head tone and a jingle tone. And a tam-tam produces a tone composed of a top drum head tone and a bottom drum head tone. It should be noted here that when the snare drum is beaten softly the snare tone sounds louder than the drum tone. On the contrary, when the snare drum is beaten strong the drum tone sounds louder than the snare tone. Like this, relative intensity in volume of the respective tone sources is not constant but variable according to tone volume of the plural-tone-source rhythmic instruments.
In a conventional automatic rhythm performing apparatus, such plural-tone-source rhythmic tone as a snare drum tone is produced based on data obtained from a sampled waveform of a tone actually produced by a snare drum and stored in an associated waveform memory. The data stored in the waveform memory may be replaced by data representing a waveform of a composite tone signal obtained by combining a drum tone signal with a snare tone signal. This conventional automatic rhythm performing apparatus is disadvantageous however in that when volume of the snare drum tone is to be increased or decreased by controlling level of a signal generated from the waveform data, volume of the drum head tone and volume of the snare tone vary at the same rate, so that the snare drum tone sounds odd. The same is true with the other rhythmic tones of plural-tone-source instruments such as a tambourine and a tam-tam.